Field of the Invention
The present invention relates to a crankshaft machining system for machining a crankshaft and a crankshaft machining method of machining a crankshaft.
Background Art
In general, a crankshaft is fabricated by machining a crankshaft of a material state (hereinafter referred to as “a crankshaft blank”) with reference to a pair of center holes. For example, according to a method described in Japan Laid-open Patent Application Publication No. 2010-29994, a crankshaft is formed as follows. First, a balance center axis of a crankshaft blank is found out by rotating the crankshaft blank and measuring its shape with a balance meter. Next, using a center hole boring device, center holes are bored in the crankshaft blank at intersections between both end surfaces of the crankshaft blank and the balance center axis. Thereafter, using one or more types of cutting devices, main journals and pin journals of the crankshaft blank are cut with reference to the center holes.
In a step described in Japan Laid-open Patent Application Publication No. 2010-29994, the positions of the center holes can be corrected by the center hole boring device through the feedback of the rotational imbalance amount of a finished crankshaft to the center hole boring device.
However, even when the positions of center holes can be corrected by the center hole boring device with respect to a crankshaft in which the center holes have been already bored and for which cutting has been done, the crankshaft is inevitably handled as a defective product unless the rotational imbalance amount thereof falls in an allowable range after the balance correction. Furthermore, the condition of unevenness in thickness of a crankshaft blank tends to vary in accordance with the manufacturing lot of the crankshaft blanks. Hence, every time the manufacturing lot of the crankshaft blanks is changed, a large number of deficit products are inevitably produced.
The present invention has been produced in view of the aforementioned situation. It is an object of the present invention to provide a crankshaft machining system and a crankshaft machining method whereby the number of deficit products can be reduced.
Solution to Problems
A crankshaft machining system according to a first aspect includes a center hole boring device, a post-centering balance meter and a cutting device. The center hole boring device is configured to bore a pair of center holes on both end surfaces of a crankshaft blank. The post-centering balance meter is configured to measure a shape of a post-centering crankshaft blank with reference to the pair of center holes, and the post-centering crankshaft blank is the crankshaft blank having the pair of center holes bored. The cutting device is configured to cut a main journal and a pin journal of the post-centering crankshaft blank. The post-centering balance meter is configured to set a principal axis of inertia on the basis of the shape of the post-centering crankshaft blank and transmit information indicating intersections between the principal axis of inertia and both end surfaces of the post-centering crankshaft blank to the center hole boring device. The center hole boring device is configured to bore a pair of center holes on both end surfaces of another crankshaft blank to be loaded next on the basis of the information that indicates the intersections and is transmitted thereto from the post-centering balance meter.
According to the crankshaft machining system of the first aspect, prior to cutting of the main journal and the pin journal of the post-centering crankshaft blank, ideal center hole positions can be comprehended on the basis of the principal axis of inertia with reference to the pair of center holes. Hence, a pair of center holes can be accurately bored in respective crankshaft blanks to be loaded thereafter. Consequently, the number of crankshafts to be handled as deficit products can be reduced.
In the crankshaft machining system according to the first aspect, the post-centering balance meter may be configured to transmit additional machining information to the cutting device, and the additional machining information indicates a machining position on and a machining amount of a counterweight of the post-centering crankshaft blank, which are required for matching a straight line connecting the pair of center holes with the principal axis of inertia on the basis of the shape of the post-centering crankshaft blank. The cutting device is herein configured to machine the counterweight on the basis of the additional machining information. With the configuration, imbalance can be removed from the post-centering crankshaft blank by matching a center hole reference axis with the principal axis of inertia. Hence, the post-centering crankshaft blank used for generating center hole positional information for correction can be also utilized as a non-defective product.
A crankshaft machining method according to a second aspect includes the steps of boring a pair of center holes on both end surfaces of a crankshaft blank; measuring a shape of a post-centering crankshaft blank with respect to the pair of center holes, the post-centering crankshaft blank being the crankshaft blank having the pair of center holes bored therein; setting a principal axis of inertia on the basis of the shape of the post-centering crankshaft blank; and boring a pair of center holes on both end surfaces of another crankshaft blank to be loaded next on the basis of information indicating intersections between the principal axis of inertia and both end surfaces of the post-centering crankshaft blank.
According to aspects of the present invention, it is possible to provide a crankshaft machining system and a crankshaft machining method whereby the number of deficit products can be reduced.